What is the oxidation number of the element ge in the compound geo2?

Oxygen has an oxidation state of - 2 so considering that there are 2 oxygen atoms,

2 x - 2 = - 4

The compound is neutrally charged so the sum of all the oxidation states must be zero. Therefore the oxidation state of Ge must be + 4 in order to cancel the - 4 to make zero.